The present invention relates to a method for preparing indigestible and low-caloric polysaccharides and, more particularly, to a method for preparing heteropolysaccharides preferably suited for indigestible and low-caloric edible materials.
As for the preparation of indigestible polysaccharides, the following methods have been suggested so far: the one to produce edible condensed polymers from an aqueous solution containing saccharides such as glucose or maltose, edible polycarbonic acid and/or edible polyol (Japanese Patent Publication (Examined) No.53-47280); the one to act upon starch or starch derivatives with an edible acid under a particular condition (Japanese Patent Publication (Examined) No.56-29512); and the one to heat up starch or starch hydrolyzates with sugar alcohol and an inorganic acid or organic acid in an anhydrous condition (Japanese Patent Publication No.1-12762). These polymers are generally obtained through polymerizing starch or starch hydrolyzates, saccharides such as glucose or maltose, and edible polycarbonic acid or polyol at a high temperature. Another method to utilize pyrodextrin with indigestibility has also been proposed (Japanese Patent Application No. 63-254540).
The results gained through these prior methods, however, are homopolymers mainly consisting of glucose and have a defect of being apt to be decomposed by amylase.
On the other hand, the research on hetero-oligosaccharides such as fructo-oligosaccharides, galacto-oligosaccharides, and bean oligosaccharides as low-caloric sweetening agents has lead to their commercial supply on the market place.
The inventors of the present application have directed their attention to the fact that these low-caloric oligosaccharides are of heterosaccharides and hit upon a new idea that indigestible polysaccharides may be obtained by converting starch decomposed products into heteropolysaccharides and, on the basis of this new idea, they have successfully come to develop a novel method for preparing heteropolysaccharides.